1. Field of the Invention
The invention relates generally to seal assemblies of the type that are used within electrical submersible pumps (ESP's) in wellbore. In particular aspects, the invention relates to techniques for monitoring operational parameters of such devices using fiber optics.
2. Description of the Related Art
Electrical submersible pumps (ESPs) are routinely used in the production of hydrocarbon from wells. A typical ESP includes a downhole motor that generates electric power used to operate a pump device. A seal assembly is typically provided between the motor and the pump. The seal includes an outer housing and a central shaft that is used to transmit torque from the motor to the pump. The seal equalizes fluid pressure so that the inside of the motor and seal are at equal pressure with the wellbore or outside environment. The seal usually provides a series of labyrinth or barrier chambers and mechanical face seals on its shaft to prevent or slow ingress of well fluids from the seal head to the motor. The seal also carries the pump down-thrust on a hydrodynamic thrust bearing so that it isn't transferred to the motor. In addition, the seal allows for motor oil thermal expansion and contraction and transfers shaft torque from the motor to the pump.
During operation, a seal assembly can be prone to failure or degradation in performance due to heating problems, component misalignment, differential pressures and so forth. Friction between the shaft and components within the housing of the seal may cause excessive heating in spots.